shy fish

Hi all, We've recently aquired some wonderful looking Panda loaches, 6 in total. They're in with some guppies, rainbow fish and glass catfish. When it comes to feeding them, we're researched what to feed however we're having the problem of the other fish gobbling everything up before it settles...

I bought a common goldfish from the store, about 5 inches tail to mouth, Its Hiding the last day or two. Is this normalÉ and also there is a feeder goldfish in there that is more friendly and they were purchased at th same time. 

Ive recently added 4 small parrot fish to my 155ltr tank. They hide all the time and the other fish are now hiding with them. Anyone any ideas why? What to do? Jonnyf